U.S. Pat. No. 3,523,891 for Electrolytic Sewage Treatment System And Process discloses an apparatus in which a dissolvable iron electrode is employed to treat sewage wastes. The system includes spaced metal electrode plates connected to a power supply for producing multi-valent metallic ions and hydroxyl ions during treatment of waste waters. The metallic and hydroxyl ions form a floc which floats to the surface of the cell and entraps suspended solids forming a supernatant frothy sludge.
I have recently been working in the field of electrolytic treatment of oil waste water in an effort to decrease the cost and increase the production capacity and efficiency of such treatment systems. I have found that when one treats oily waste waters by dissolving iron electrolytically into such waste waters, it is necessary generally to have a ferrous ion to oil weight ratio of about 0.05 in order to get good separation. As this high ferrous ion to oil ratio, it is, of course, necessary to expend a good deal of electrical energy in order to obtain the required amount of dissolved iron in the wastes. The cost of purchasing power to dissolve the iron has to be taken into account as a part of the overall cost of the process.
Another important item is the time of processing. For example, to break a typical emulsion of oil waste water effectively within a thirty-minute period, the ferrous ion to oil weight ratio produced by the dissolved iron electrode has to be in excess of 0.05. When the ferrous ion to oil weight ratio is about 0.035, it takes well over twenty-four hours to break the emulsion and obtain water of acceptable quality. It must be kept in mind that the breakup time is measured from the time that the oil emulsion has the specified amount of iron therein.
It is an object of my invention to provide a method for increasing the rate at which an emulsion of oil in water will break at lower ferrous ion/oil concentrations.
It is a further object of my invention to provide a method of breaking oil-in-water emulsions which is simple and efficient in operation, and economical to carry out because of reduced power requirements.